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Description: A high-energy CO{sub 2} laser is channeled in a capillary discharge. Plasma dynamic simulations confirm occurrence of guiding conditions at the relatively low axial plasma density 1 {divided_by} 4 x 10{sup 17} cm{sup -3}. A relativistic electron beam transmitted through the capillary changes its properties depending upon the plasma density. We observe focusing, defocusing or steering of the e-beam. Counter-propagation of the electron and laser beams in the plasma channel results in generation of intense picosecond x-ray pulses.
Date: June 23, 2002
Partner: UNT Libraries Government Documents Department

An advanced open-path atmospheric monitor design

Description: The conceptual design of an open-path atmospheric monitor combines an acousto-optic tunable filter for emission spectroscopy (3-14 {mu}m) with a mid-IR (4.6-5.4 {mu}m) for absorption spectroscopy. It utilizes mostly commercially available components, covers a large area ({approximately}4 km radius), measures the distance to any reflecting object, can take measurements along any line-of-sight, and is eye safe. Of twenty test pollutants it is to detect, the concentrations of all twenty will be measurable via emission spectroscopy and ten by the more sensitive absorption spectroscopy.
Date: May 1, 1996
Creator: Taylor, L.; Suhre, D. & Mech, S.
Partner: UNT Libraries Government Documents Department

Electron acceleration in preformed plasma channels with terawatt CO{sub 2} laser

Description: Extended cylindrical plasma channels produced under gas breakdown by axicon-focused laser beams may be used as optical waveguides in laser-driven electron accelerators. Plasma channeling of the laser beams will help to maintain a high acceleration gradient over many Rayleigh lengths. In addition, the rarefied gas density channel produced after the optical gas breakdown, and followed by a plasma column expansion, reduces multiple scattering of the electron beam. A high-power picosecond C0{sub 2}laser operational at the ATF and being further upgraded to the 1 TW level is considered as the source for a plasma channel formation and as the laser accelerator driver. We show how various laser accelerator schemes including beat wave, wake field, and Inverse Cherenkov accelerator benefit from using a channeled short-pulse C0{sub 2}laser as a driver.
Date: February 1, 1995
Creator: Pogorelsky, I.V.
Partner: UNT Libraries Government Documents Department

Tritium Removal by CO{sub 2} Laser Heating

Description: Efficient techniques for rapid tritium removal will be necessary for ITER (International Thermonuclear Experimental Reactor) to meet its physics and engineering goals. One potential technique is transient surface heating by a scanning CO(subscript 2) or Nd:Yag laser that would release tritium without the severe engineering difficulties of bulk heating of the vessel. We have modeled the heat propagation into a surface layer and find that a multi-kW/cm(superscript2) flux with an exposure time of order 10 msec is suitable to heat a 50 micron co-deposited layer to 1,000-2,000 degrees. Improved wall conditioning may be a significant side benefit. We identify remaining issues that need to be addressed experimentally.
Date: October 1, 1997
Creator: Doyle, B.L.; Skinner, C.H.; Mueller, D.; Kugel, H. & Wampler, W.R.
Partner: UNT Libraries Government Documents Department

Application of coherent lidar to ion measurements in plasma diagnostics

Description: A coherent lidar system has been constructed for the measurement of alpha particles in a burning plasma. The lidar system consists of a pulsed CO{sub 2} laser transmitter and a heterodyne receiver. The receiver local oscillator is a cw, sequence-band CO{sub 2} laser operating with a 63.23 GHz offset from the transmitter.
Date: March 1, 1997
Creator: Hutchinson, D.P.; Richards, R.K.; Bennett, C.A. & Simpson, M.L.
Partner: UNT Libraries Government Documents Department

CO{sub 2} laser technology for advanced particle accelerators

Description: Short-pulse, high-power CO{sub 2} lasers open new prospects for development of ultra-high gradient laser-driven electron accelerators. The advantages of {lambda}=10 {mu}m CO{sub 2} laser radiation over the more widely exploited solid state lasers with {lambda}{approximately}1 {mu}m are based on a {lambda}{sup 2}-proportional ponderomotive potential, {lambda}-proportional phase slippage, and {lambda}-proportional scaling of the laser accelerator structures. We show how a picosecond terawatt CO{sub 2} laser that is under construction at the Brookhaven Accelerator Test Facility may benefit the ATF`s experimental program of testing far-field, near-field, and plasma accelerator schemes.
Date: June 1, 1996
Creator: Pogorelsky, I.V.
Partner: UNT Libraries Government Documents Department

Gas breakdown limits for inverse Cherenkov laser accelerators

Description: The probability of avalanche, tunneling and multiphoton ionization induced by a CO{sub 2} laser in H{sub 2} gas has been calculated. Laser light screening by a self-induced plasma density gradient is considered as the limiting factor for upscaling a CO{sub 2} laser-driven Inverse Cherenkov Laser Accelerator beyond 650 MeV/m. However, in near-resonance inverse Cherenkov acceleration where a shorter wavelength laser is used at a wavelength near the resonance of the gas (e.g. 248nm in H{sub 2}), the formation of a plasma is not a problem because the plasma density is below the critical density. In that case, the laser beam propagates unaffected through the plasma and the acceleration gradient is not limited by gas breakdown. Gradients > 1 GeV/m are possible.
Date: July 1, 1995
Creator: Liu, Y. & Pogorelsky, I.V.
Partner: UNT Libraries Government Documents Department


Description: A high-energy CO{sub 2} laser is channeled in a capillary discharge. Occurrence of guiding conditions at a relatively low plasma density (<10{sup 18} cm{sup -3}) is confirmed by MHD simulations. Divergence of relativistic electron beam changes depending on the plasma density. Counter-propagation of the electron and laser beams inside the plasma channel results in intense x-ray generation.
Date: November 12, 2002
Partner: UNT Libraries Government Documents Department


Description: Several proof-of-principle laser accelerator experiments turned a long-wavelength of a CO{sub 2} laser to advantage. Ongoing advancement to multi-terawatt femtosecond CO{sub 2} lasers opens new venues for next-generation laser acceleration research.
Date: December 3, 2001
Partner: UNT Libraries Government Documents Department

Design analysis for a 100-MeV inverse Cerenkov laser accelerator

Description: The analysis of a 100-MeV demonstration experiment based upon inverse Cerenkov acceleration (ICA) is presented. This experiment would use the Accelerator Test Facility (ATF) at Brookhaven National Laboratory. With 50-GW of delivered laser peak power from the ATF CO{sub 2} laser, our analysis indicates the 65-MeV ATF e-beam can be accelerated to >165 MeV using three stages of acceleration in {approximately}1 m of total length. The number of electrons accelerated can be raised to {approximately}10{sup 9} by prebunching the e-beam using an already available device.
Date: December 31, 1993
Creator: Fontana, J. R.; Kimura, W. D.; Steinhauer, L. C. & Pogorelsky, I.
Partner: UNT Libraries Government Documents Department

Computational methods for describing the laser-induced mechanical response of tissue

Description: Detailed computational modeling of laser surgery requires treatment of the photoablation of human tissue by high intensity pulses of laser light and the subsequent thermomechanical response of the tissue. Three distinct physical regimes must be considered to accomplish this: (1) the immediate absorption of the laser pulse by the tissue and following tissue ablation, which is dependent upon tissue light absorption characteristics; (2) the near field thermal and mechanical response of the tissue to this laser pulse, and (3) the potential far field (and longer time) mechanical response of witness tissue. Both (2) and (3) are dependent upon accurate constitutive descriptions of the tissue. We will briefly review tissue absorptivity and mechanical behavior, with an emphasis on dynamic loads characteristic of the photoablation process. In this paper our focus will center on the requirements of numerical modeling and the uncertainties of mechanical tissue behavior under photoablation. We will also discuss potential contributions that computational simulations can make in the design of surgical protocols which utilize lasers, for example, in assessing the potential for collateral mechanical damage by laser pulses.
Date: February 1, 1994
Creator: Trucano, T.; McGlaun, J. M. & Farnsworth, A.
Partner: UNT Libraries Government Documents Department

Picosecond CO{sub 2} laser for relativistic particle acceleration

Description: A table-top 20-GW 50-ps CO{sub 2} laser system is under operation at the Brookhaven Accelerator Test Facility. We compare laser performance with model predictions. Extrapolations suggest the possibility of compact terawatt CO{sub 2} laser systems suitable as laser accelerator drivers and for other strong-field applications. Latest progress on an Inverse Cherenkov Laser Accelerator experiment is reported.
Date: June 1, 1994
Creator: Pogorelsky, I.; Ben-Zvi, I.; Kimura, W. D.; Kurnit, N. A. & Kannari, F.
Partner: UNT Libraries Government Documents Department

High-intensity laser synchrotron x-ray source

Description: A laser interacting with a relativistic electron beam behaves like a virtual wiggler of an extremely short period equal to half of the laser wavelength. This approach opens a route to relatively compact, high-brightness x-ray sources alternative or complementary to conventional synchrotron light sources. Although not new, the Laser Synchrotron Light Source (LSLS) concept is still waiting for a convincing demonstration. Available at the BNL`s Accelerator Test Facility (ATF), a high-brightness electron beam and the high-power C0{sub 2} laser may be used as prototype LSLS brick stones. In a feasible demonstration experiment, 10-GW, 100-ps C0{sub 2} laser beam will be brought to a head-on collision with a 10-ps, 0.5-nC, 70 MeV electron bunch. Flashes of well-collimated, up to 9.36-keV ({approximately}{Angstrom}) x-rays of 10-ps pulse duration, with a flux of {approximately}10{sup 19} photons/sec will be produced via linear Compton backscattering. The x-ray spectrum is tunable proportionally to a variable e-beam energy. A natural short-term extension of the proposed experiment would be further enhancement of the x-ray flux to a 10{sup 21}{minus}10{sup 22} photons/sec level, after the ongoing ATF CO{sub 2} laser upgrade to 1 TW peak power and electron bunch shortening to 3 ps. The ATF LSLS x-ray beamline, exceeding by orders of magnitude the peak fluxes attained at the National Synchrotron Light Source (NSLS) x-ray storage ring, may become attractive for certain users, e.g., for biological x-ray microscopy. In addition, a terawatt CO{sub 2} laser will enable harmonic multiplication of the x-ray spectrum via nonlinear Compton scattering.
Date: October 1, 1995
Creator: Pogorelsky, I.V.
Partner: UNT Libraries Government Documents Department

An inverse free electron laser accelerator: Experiment and theoretical interpretation

Description: Experimental and numerical studies of the Inverse Free Electron Laser using a GW-level 10.6 {mu}m CO{sub 2} laser have been carried out at Brookhaven`s Accelerator Test Facility. An energy gain of 2.5 % ({Delta}E/E) on a 40 MeV electron beam has been observed E which compares well with theory. The effects on IFEL acceleration with respect to the variation of the laser electric field, the input electron beam energy, and the wiggler magnetic field strength were studied, and show the importance of matching the resonance condition in the IFEL. The numerical simulations were performed under various conditions and the importance of the electron bunching in the IFEL is shown. The numerical interpretation of our IFEL experimental results was examined. Although good numerical agreement with the experimental results was obtained, there is a discrepancy between the level of the laser power measured in the experiment and used in the simulation, possibly due to the non-Gaussian profile of the input high power laser beam. The electron energy distribution was studied numerically and a smoothing of the energy spectrum by the space charge effect at the location of the spectrometer was found, compared with the spectrum at the exit of the wiggler. The electron bunching by the IFEL and the possibility of using the IFEL as an electron prebuncher for another laser-driven accelerator were studied numerically. We found that bunching of the electrons at 1 meter downstream from the wiggler can be achieved using the existing facility. The simulation shows that there is a fundamental difference between the operating conditions for using the IFEL as a high gradient accelerator, and as a prebuncher for another accelerator.
Date: June 1, 1997
Creator: Fang, Jyan-Min
Partner: UNT Libraries Government Documents Department